Plugins in data/plugins are loaded at startup and can add a tab with a read-only node board, and the demo plugin shows every asset as a node (#113)

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tools/seed-e2e.mjs

@@ -6,6 +6,8 @@
  *
  * Usage: node tools/seed-e2e.mjs [projectId] [baseUrl]
  */
+import { copyFileSync, mkdirSync, readdirSync } from 'node:fs';
+import { fileURLToPath } from 'node:url';
 import { sineWav } from './lib/audio.mjs';
 import { edge, node, port, sceneObject, variable } from './lib/builders.mjs';
 import { PROJECTS, cliArgs, uploadFont, uploadSound, writeProject } from './lib/projects.mjs';
@@ -13,6 +15,16 @@ import { adjustColorsShader } from './lib/shaders.mjs';
 
 const { projectId, baseUrl } = cliArgs('seed-e2e.mjs', PROJECTS.fixture);
 
+/**
+ * The plugins that ship with the repository, where the editor loads them from – the build does the
+ * same, this makes a run after a plain checkout independent of it. The server is this checkout
+ * (locally and in CI), so a file copy is enough.
+ */
+const ROOT = fileURLToPath(new URL('..', import.meta.url));
+mkdirSync(`${ROOT}data/plugins`, { recursive: true });
+for (const file of readdirSync(`${ROOT}plugins`).filter((f) => f.endsWith('.js')))
+  copyFileSync(`${ROOT}plugins/${file}`, `${ROOT}data/plugins/${file}`);
+
 /**
  * Two typefaces for the font step to pick and to drop. They are put on the server but not made
  * into assets: the step is about the picker and the drop making them. The files come from the